For example, Japanese Unexamined Patent Application Publication No. 8-196950 (Patent Literature 1), or WO01/02099 (Patent Literature 2) disclose a coating material nozzle of a spray gun, which is formed with, for example, four air grooves disposed on a periphery of a coating material ejection opening of a tip end portion of the coating material nozzle at equal spaces. Each air groove is formed to have a cross section of, for example, a V shape, and increases in depth toward a tip of the coating material nozzle.
When a coating material is ejected from the coating material ejection opening of the coating material nozzle, a compressed air is introduced to the air grooves from a body. The air grooves are designed such that the compressed air increases in gas-liquid contact area while passing through the grooves, and then mixes with the ejected coating material by collision. As a result thereof, even if the compressed air was in a state of air flow under a low pressure, the ejected coating material can be effectively atomized toward a central portion thereof.
At the tip end portion of the coating material nozzle, an air cap is disposed to define a slit in the form of a ring shape between the tip end portion and the air cap. It is configured such that the compressed air is introduced from a side of the body behind the air cap to the slit and the air grooves of the coating material nozzle.